Automatic infeeding mechanism for grinding machines



All@ 25, 1942. R; D. WORTENDYKE Erm. 2,294,255

AUTOMATIC INFEEDING MECHANISM FOR GRINDING MACHINES ATTORNEY.

AUZ- '25, 1942- RQ D. WQRTENDYKE Erm. 2,294,265

AUTOMATIC INFEEDING -ldEGIIANISl-H `FOR GRINDING MACHINES 3 sheets-smet 3 Filed Aug. 4. 1941 b NNNHNI ATTO/YEX Patented` Aug. 25, 1942 UNITED STATES PATENT OFFICE AUTOMATIC INFEEDING MECHANISM FOR GRINDING MACHINES Raymond D.

Wortendyke, Cincinnati, and

Application August 4, 1941, Serial No. 405,362

15 Claims.

This invention relates to machine tools and more particularly to improvements in grinding machines.

One of the objects of this invention is to provide improvements in automatic infeeding mechanisms for grinding machines.

Another object of this invention is to provide improved means for power actuating a manually operable infeed control lever of a grinding machine.

A further object of this invention is to provide an automatic infeed cycle control attachment for grinding machines which will convert a manual control infeed mechanism into an automatic cycle controlled mechanism.

Other objects and advantages of the present invention should be readily apparent by reference to the following speciiication, considered in conjunction with the accompanying drawings forming a part thereof and it is to be understood that any modifications may be made in the exact structural details there shown and described, within the scope of the appended claims, without departing from or exceeding the spirit of the invention.

Referring to the drawings in which like reference numerals indicate like or similar parts:

Figure 1 is an elevational View partly in section of the attachment comprising this invention.

Figure 2 is a sectional view on the line 2-2 of Figure 1.

Figure 3 is a detail view of a manual control lever as viewed on the line 3-3 of Figure 1.

Figure 4 is a sectional view on the line 4-4 of Figure 1.

Figure 5 is a diagrammatic view of the hydraulic control circuit of this invention.

Figure 6 is a fragmentary transverse sectional View of one form of grinding machine in conjunction with which the present invention is adapted to be employed.

This invention is particularly applicable to a grinding machine of the type disclosed in United States Patent No. 2,101,644, issued December '7, 1937, and the reference numeral I0 in Figure 1 of the drawings indicates the saddle of such a machine. This saddle, as disclosed in the patent, carries the work and is bodily movable on the bed A toward and from a cutting tool such as the grinding wheel D for effecting a grinding operation. Such movement may be eiected by rotating a screw II, Figures 5 and 6, which has one end threaded in a nut IIa which is axedwith the bed A of the machineand thev 5.5

other end slidably journaled in a bearing I2 carried by the saddle I0.

The tool or grinding wheel D is carried by the column or tool support E rising from the rear portion of the bed or support A. The saddle I is supported on the bed for in and out movement and is provided at its forward portion with the ways B for the translatable table or work support C which is in turn provided with work holding means indicated in .part at F. It will thus be noted that due to the position of the work support on the upper forward portion of the saddle I0, it is relatively movable with respect to the tool support E and in a direction toward and from said support with the saddle as controlled by the screw II and the piston cylinder or motor structure I4-I5 as hereinafter described.

The screw has a reduced portion I3 to which is fitted a piston I4, the piston being slidably mounted in a cylinder I5. It will be obvious that during rotation of the screw that pressure must be maintained in one end of the cylinder I in order that the screw may impart movement to the saddle. The screw adjustment is utilized more particularly with a pick feed mechanism during traverse grinding but is not suitable for automatic infeed grinding operations. Therefore, the piston and cylinder arrangement is provided for infeeding operations because by admitting pressure to port I6 and connecting port Il to exhaust the saddle may be moved quickly to eiTect engagement between the work and grinding wheel after which, by properly controlling the rate of flow, the movement may be continued at a slower rate to effect the grinding operation.

The admittance of fluid pressure to the cylinder I5 is controlled by a servo-valve indicated generally by the reference numeral I8 and this Valve has a plunger I9 in which is formed two grooves and ZI for alternately connecting a pressure port 22 with motor ports 23 and 24 which are connected by channels 25 and 26 to the cylinder ports I6 and I1 respectively. The pressure port 22 is continuously supplied with pressure by suitable means such as the pump 21 having an intake 28 through which fluid is withdrawn from a reservoir 29. The exhaust ports 30 and 3| of the servo-valve are connected by a return line 32 to the reservoir.

The servo-valve plunger I9 is continuously urged in one direction by a spring 33 which holds the valve plunger into contact with one end of a lever 34 which is pivotally connected at an intermediate point 35 to a plunger 36, and at they other end to the screw ll by means of a shifter groove 31'into which the ball-shaped end 38 of the lever fits.

The plunger 35 is held against rotation and is surrounded by a rotatable sleeve 39 to which it is operatively connected by pin 48 engaging cam slot 4l. The cam slot 4I' is angularly arranged with respect to the axis of the sleeve and plunger whereby rotation of the sleeve will eiect axial movement of the pin and thus of the plunger 35.

A manual control lever 4,2 is attached to the sleeve 39 for imparting rotation thereto and thereby effecting reciprocation of the plunger 96.

The cam slot il is so angularly arranged that when the lever 42 is rotated Ain acl'ockvvise vdirection as viewed in Figure 5, the plunger 35 is axially shifted to cause clockwise rotation of the lever 34 about its pivot 38, thereby shifting the servo-valve plunger I9 is a. direction to connect pressure port 22 with port 23 whereby pressure iuid is admitted to the cylinder lv at the port l5. This will cause the saddle toY movey toiward the Ygrinding wheel. When the lever 4Z' is returned in aV counterclockwi'se direction, the lever 34 is rotated in a clockwise direction by the plunger 35, thereby connecting pressure port 22 toport 29, causing theadmission of fiuid pressure toithe cylinder l5 at 'the .port Il.. This will cause movement of the saddle away from the grinding wheel.A It will .be noted that the lever 312 is moved in av direction opposite to the subsequently desired movement of the saddle.

When the saddle moves,v the servo-valve sleeve andthe pivot point 35 move together causing return movement of the. plunger in the same direction asv the sleeve and pivot point move but due to the lever advantage the plunger moves faster than the sleeve and eventually closes the pressure port, thus producing/the necessary follow-up. movement.

This invention is directed to an inte-ed Vcycle control uni-twhich may be attached to the iront of the saddle for automatically eiect'ing movement of the lever 42, causing it to be rotated in one direction rst at a fast or rapid. traverse rate andthen at a slow or grinding rate, auto"- matically reversed and subsequently returned toy a starting position; It;` is` necessary, however, that 'the operator rotate the lever 82,' through asmall 'predetermined a'ngle inrorder to start the automatic cycle.

Attention isV invited to the fact that the machine-isvprovided with a selector valve t3- having a plunger 44 and thisplunger is positioned' as shownin Figure 5 when it isl desired to select theinieed cycle.

This valve has two ports ll5 and' lf3 which are connected by channels 4l and 4'8" to vports 99 and 55` of the sleeve 319. The plunger 35 has an annular groove -5-I for connecting a pressure port 52 alternately tothe ports 49 and 55. rThe port 52 is continuously supplied with pressureV from the pump 2l by a branch line 53 leading from; the pressure port 22 of the servo-valve I8. When the mechanism is in a starting position thefpressure por-t '52! is connected to the port i9E but -since the port i5 is blocked in the valve "43 no action takes place. The handle 42 must be rotated a sui'cient 'amount to shift the plunger 35 and connect the pressure port 52V tothe portV 50 in order to start the automatic cycle.

When; these connections are established. the pressure fluid flows Vthrough the line t8 tothe port t6. ofthe valve `4'3 which is interconnected or pressure in this line to eiect shifting of a plunger 58 in a starting valve 59 located in the valve body 6i) of the attachment to start operation of the automatic cycle.

As shown in Figure 5, the plunger 58 is normally held in the position shown by a spring 5]; This valve has a pressure port 62 which is connected by flexible tubing or other means to the pump 2 and a plurality of exhaust ports 69 and 85 which are all connected to a common return line 65.

When lthe plunger 58 is moved down by the incoming pressure in line 55 the port 52V is Aconnected by an annular groove 5l in the plunger to a port 58 and this port is connected' by flexible channel means 69 to a plurality of ports lil, ll, 'l2 and 'I3 in the actuating cylinder lli pivotally supported at l onA the' saddle'. The cylinder contains a piston l5 that is operatively connected by the piston rodl l5 tothe manual control lever 42.

It will be noted that it was necessary to rotate the lever 122 to a predetermined angle in order to effect the pressure connectionto line 95 and this rotation of the leverVv moves the piston l5 downward a suihcient amount to close thev port il and open the port l andj this is'the condition of these ports at theV time that the pressure connection is made to line 99. It will now be obvious that the uid pressure may enter the port 'Hl so as. to start the power movement of lever 42.

The iuid in the' lower end of cylinder T4 exhausts through port 11,. channel 'I8 and interconnected ports 'I9 and 8!)Y of a. reversing valve, indicated generally by the reference numeral 8|, to channel 82. This channel has a branch connection 83 to port 84 of a by-pass orY rapidv traverse control valve, indicated generally by the reference numeral 85 andv including' a plunger 85. The channel 83 has a check valve 8l serially arranged therein and so directed 'that pressure in line 82 will open the check valve.

The valve plunger 85 hasan annular groove 88 for interconnecting port 84' with an exhaust port` B9. A-t the beginning of the cycle the plunger 85 is held downward against the resistance of a spring 99 in a position to` interconnect ports 84 and 89 and thereby form alow resistance .path tor reservoir from the' cylinder Mp The plunger 86 is 'actually held in this position by a rapid traverse control. cam 9|` which isattached to the hub 92 of the control'lever` 42 as by bolts 93. By means of the elongatedV slots 94 in the cam plate 9l the cam may be rotatably adjusted relative tothe lever in order to adjust the rate changey point 95 of the rapid traverse cam and; thus determine the point during the. travel'of. the piston-1.5.atwhich the rate ofimovement will. change from'. rapid traverse toie'ed'. In other words, at the point 95.' the cam falls away rapidlyV to the inactive portion 95 of. the cam', permitting the plungerA 851 to rise under the urge of the spring'tlll and thereby close theport 892.

The closingof portl 89: forcesv the fluid in chan'.- nel' 82"toi traverse a. new path comprising ports;

91 and 98, of a manually rotatable valve 99 which is normally in a position that a cross bore in the plunger interconnects ports 91 and 98. A channel |0| connects port 98 to port |02 of the starting valve 59, the plungerl 50 of which is in a position that the annular groove |03 in the plunger connects port |02 to port |04. The fluid continues through this port and channel |05 to port |06 of an infeed rate control valve, indicated generally by the reference numeral |97.

This valve has a plunger' |08 which is threadedly connected at |09 to the housing whereby rotation of the plunger by the knurled knob H0 will adjust the V-notch relative to the port |06 and thereby control the rate of flow through the valve. The fluid collects in the upper chamber ||2 and passes through port H3, channel |4 to port ||5 of the starting valve, which port is part of the annular groove 64 so that regardless of the position of the plunger 58 the uid will continue through the groove to the exhaust line 66.

It will now be apparent that the closing of the rapid traverse valve changes the rate of movement of the piston from a rapid traverse movement to a feed movement. It will be obvious that the setting of the rapid traverse cam makes the rate change point uniform for each cycle and does not allow for variations in the size of work coming to the machine. In other words, the cam must be set to suit the largest size of work coming to the machine and some time would be lost when work smaller than the maximum comes to the machine. In order to eliminate this lost time, provision is made whereby the operator may press on the lever 42 and thus accelerate the movement until the grinding wheel engages the work and begins to spark. This adds yversatility to the device.

This is made possible by providing a runahead valve ||6 having a plunger |I'| normally held in the position shown by a spring |8. This valve has a port ||9 which is connected by channel to the annular groove port |05 of the rate valve whereby when the pressure in this groove rises beyond or overcomes the resistance of spring ||8 the plunger is forced downward a suicient amount to interconnect port |9 with port |2| whereby the fluid may return through channel |22 to the chamber ||2 of the rate valve, thus bypassing the resisting groove permitting a greater amount of uid to exhaust through the line ||4 which is necessary in order that the piston 15 may move at a more rapid rate.

After the grinding Wheel is in grinding relation with the work the feeding movement continues at the rate determined by the rate valve until the grinding operation has been completed or, in other words, until the servo-motor piston |4 has reached the end of its stroke. Positioned so as to be timed with this, is a rise |23 on another cam |24 integral with the hub 92 of the control lever 42 which rise actuates the plunger 'I6 to open the rapid traverse valve, thus short-circuiting the return line 82 to reservoir again, permitting the piston 'l5 to move at a rapid rate for a short distance, thereby opening the servo-valve without a compensating follow-up movement due to the fact that the piston I4 is at the end of its cylinder. This causes a rise in pressure in the cylinder l5 firmly holding the saddle against what might be termed a positive stop. After this has been accomplished, the piston l5 engages the end of a reversing valve plunger |25 which is located in the end of the cylinder-14 and shifts it against the resistance of a spring |26.

A small movement of the reversing plunger will crack the port 'l2 which is under pressure at this time and the fluid pressure will rush into the chamber |2'| and continue the movement due to the fact that the spool |28 on the valve is larger in diameter than the spool |29 which produces a diiferential effect. Any fluid in the space |30 below the Valve will exhaust freely through the port |3| and branch line |32 to the annular groove port 80 and thus to reservoir until the port |30 is closed by the plunger. It will be seen that the operation up to this point, is that the piston rotated the lever at a fast rate to bring the grinding wheel ino the work, then rotated it at a slow rate to effect the. grinding operation which operation terminated when the piston I4 reached the end of its cylinder. The lever 42 was still capable of a small additional movement, and during this movement, the rapid traverse valveY was vopened and the reversing valve was shifted resulting in a short fast movement of the lever which opened the servo-valve to firmly hold the saddle against its positive stop which movement also shifted the reversing valve sufliciently to start its own movement independent of the lever actuating piston which is necessary because the piston is stopped from further movement by the lever engaging the positive stop |43.

The movement of the reversing valve is retarded by a tarry valve in the following manner.

The :duid is forced through the port |33 and channel |34 to port |35 of a tarry valve indicated generally by the reference numeral |36. This valve has an adjustable plunger |37 which is threadedly connected at |38 to the valve and rotatably adjusted by the knurled knob |39 to set the position of the resistance V-groove |40 relative to the port |35 to control the rate of escape of the fluid through the valve and thereby regulate the amount of tarry of the reversal. The

' fluid escaping through the valve accumulates in Vthe chamber |4| and passes through line |42 back to the annular groove and return line 82.

As the reversing valve continues to move, a groove |44 in the valve registers with port |3I. In this groove are radial holes |45 which communicate with the spring bore |45 for spring |23, thus forming a by-pass around the tarry valve, the fluid in chamber |39 now escaping through the spring bore |45, radial holes |45, groove |44, port |3| and channel |32 to the exhaust groove 90. This permits a, quick movement of the reversing valve plunger which is sufcient to completely and quickly uncover the pressure port 'I3 whereby the annular groove 41 will connect port T3 to p-ort 19.

When this has been established it will be noted that the pump pressure is now connected to both ends of the cylinder 14 but since the area of the lower end of piston 'I5 is larger than the area of the upper end, the piston 'l5 will move upwards returning the lever 42 while the reversing valve plunger |25 will be prevented from returning to its normal position by the pump pressure in the lower end of cylinder 'I4 whereby the return movement of piston 'l5 can be completed without interruption.

As the lever 42 reaches th'e end of its return stroke, the plunger 35 will have been shifted sufficiently to interconnect port 50 of valve 39 to an exhaust port |48. This will connect the channel 55 which supplied the pressure for holding the starting valve in a running position to reservoir? whereby the valve plunger 58 will return under the' urge of spring 6| but in order to retard this returning movement a choke coil |49 is inserted in the line 55 so as to maintain the return movement ofv tlielever 42 long 'enough` to' close the port When the starting valve plunger is returned sufficiently to interconnect ports 58 andi 63, the' pressure in cylinder 14 isreleased and the reversi-'ng valve plunger |20 returned to i-ts starting position by the spring |26.

Ordinarily the movement of plunger |25 would tend to createa vacuum in the chamber |30, but this is prevented at the beginning of the stroke bythe fact that the groove |44 is in registry with the port |3| whereby iuid may be drawn from the return line 82 through channel |3`3 and after these parts move out of registry, fluid is drawn from the same line 82A through ch'a-nnel |42, chamber |40, check valve |`50 which isonly held closed by a light spring, annular groove |35 in the tarry valve and channel |34. Thus, all the parts have automatically returned to their starting position',

r'I-he rotatable valve 00 h'as nin addition to the cross bore |00, a second cross bore |5-| whichinterconnects the parts of channel 69. ThisY valve plunger has an operating lever |52 keyedto the lower end thereof as shown in Figures 1 and 3.

Rotation of this valve blocks the lines from ports 68 and |02 of the starting valve and interconnects parts |53V and 91 by means of longitudinal grooves |54 and |55 and annular groove |55, thereby interconnecting the ends of cylinder '|4 to permit manual operation of lever 42. This valve may also be used for emergency stop purposes.

Th'ere has thus been provided an improved automatic infeed attachment suitable for attaching to grinding machines having a manual infeed control lever for' automatically imparting movemen-t to the lever in a man-ner to effect a oomplet'e automatic infeed grinding cycle,

What is claimed is:

1. In a machine tool having a Work support land a tool support and means for effecting relative movement between the supports including a manual control lever which is oscillatable through a predetermined angle to effect a cyclic advance and retraction between said supports, theA combination of an automatic cycle control uni-t attachable to the machine, said unit having a power operable member connectible to said lever, `a source of power for said member, and meansV automatically responsive to a small manual movement of Ysaid lever to connect said source of power to' said power operable member whereby thev ini-tial manual Vmovement of the lever will be continued automatically. l

2. In a grinding machine having a work support and a grinding wheel support, means for effecting an infeeding movement lbetween said supports including a manual control lever, a cycle control unit for the lever, said unit having a iiuid operable member, a source of pressure therefor, means responsive tomanual movement of the lever for connecting said source of pressure to said uid operable member whereby the lever will be moved by power to effect an infeed grinding operation, and means automatically shiftable for reversing the direction of movement vof said member to effect return of the grinding wheel tov a starting position.

v`3. In a machine tool having a work support and a tool support, means for electing relative movement between the supports including a manual control lever, a cycle control unit jattachable to the machine andk having means ini the -unit for operating saidA lever, lmeans to control the rate and direction of movement of the lever,v a source of power, and means controlled by said lever for connecting said source of power to said cycle control unit.

4. In a machine tool having a work support and a tool support, means for effecting relative movement between the supports including a manual control lever, an automatic cycle control unitv attachable to the machine for-operating said lever, saidl unit including a fluid operable member connectible to said lever, a feed rate control valve, a cam operated valve for rendering the feed rate control valve ineffective, a source of fluid pressurer inthe machine, means operable by the lever for connecting said source to said unit, and cam means carried by said lever for operating said cam operated valve at preselected points in the cycle of lever movement.

5. In a cycle control unit for a machine tool having a manually operable cycle control lever, the combinationV of a fluid operable piston insaid unit operatively connected to said lever, said unit having a shiftable valve means for connecting a sourceof fluid pressure to said piston toV effect movement in one direction, a reversing valve, means operable by the piston for shifting said reversing Valve suihciently to stop vthe movement of the'piston, fluid operable means for continuing the shifting of said reversing valve after the piston' has stopped, a tarry control valve for controlling the timeof shifting and thereby provide a dwell in lthe movement kof said lever, and means responsive at the end of the sluiting of said reversing valve for effecting return movement of said piston.

6. In a machine tool having a work support and a tool support, means for effecting relative movement between the supports including a manual control lever, a cycle control unit attachable to the machine and having a power operabley member for moving said lever, a start and stop' valve in the unit for connecting fluid pressure to the power operable unit, a source of pressure in the machine connected to said valve, mean-s operable by the lever for connecting said source of fluid pressure for shifting said valve to start operation of the power operable member, means in the unit for automatically reversing the direction' of movement of the lever, means operable by the lever during its return movement to disconnect the shifting pressure from the start valve, resilient means for returning 'said start valve, and ya Vchoke coil for retardi'n'g the return of said start and stop valve whereby the return stroke of the lever will be greater than its power advance stroke'.

7. In a machine tool having a Work support and a tool support, means for effecting relative movement between the supports including a manual control lever, a cycle control unit attachabley to the machine, a fluid operable member in the unit connectible for shifting said lever, a source of fluid pressure connected to said uni-t, valve means in the unit for connecting said source of iiuid pressure yto the iluid operable member, a return channel from said fluid operable means including a rate control valve Vfor determining the rate of movement of said member, a reservoir by-pass valve connected to said channel, cam means carried by said lever for holding said by-pass valve open during the initial stroke 'of the fluid operable means `whereby the lever will be moved at a rapid traverse rate, said cam means being formed to permit closure of the valve after a predetermined movement of the lever to produce a feed rate, and other cam means carried by the lever for opening said valve at the end of the advance stroke of the lever.

8. In a machine tool having a work support and tool support means for eiecting relative movement between the supports including a manual control lever, a cycle control unit attachable to the machine and having a source of pressure connected thereto, said unit including a fluid operable member connectible for actuation of the lever, a start and stop valve for connecting said source of fluid pressure to said member, a throttle valve controlling the rate of exhaust from said member, separate channels for connecting each of said valves to said iiuid operable members, and an auxiliary control valve serially connected in said channels and positionable at will to block the portions of the channels leading from said valves and interconnecting the portions of the channels from said fluid operable member to permit manual operation of said lever.

9. In a machine tool having a work support a tool support and means for effecting relative movement between the supports including a manual control lever, a cycle control unit attachable to the machine, said unit containing a uid operable piston, means to connect the piston to said lever for power operation thereof, a source of fluid pressure connected to said unit, means in said unit controlled by said lever for connecting said source of iiuid pressure for operation of the piston, a reversing valve adapted to be shifted by the piston to initiate a self-energized stroke thereof, a tarry valve for controlling the rate of said stroke, and means operable by the reversing valve for short-circuiting said tarry valve whereby the final movement of the reversing valve will be at a fast rate to effect the necessary connections to cause a rapid return movement of the piston.

10. In a device of the character described, the

combination with an actuating piston, of a hypositely coupled with the piston for conveying tuation of said piston, an exhaust conduit opdraulic circuit for effecting a unidirectional achydraulic actuating medium displaced thereby, a pair of alternatively available exhaust conduits, means for eiecting low resistance to flow in one of said conduits, means lfor effecting higher resistance to ow in the other of said conduits, a selector device for determining the eiTective coupling of the piston exhaust conduit with respect to the low resistance exhaust ccnduit, whereby feed or rapid traverse movements of the piston may be effected under given actuating pressure according to the high or low resistance exhaust conduit reaction thereon, and additional means for bypassing the high pressure resistance to permit increased rate of discharge of the actuating medium by way of the high pressure resistance conduit.

11. In a device of the character described, the combination with an actuating piston, of a hydraulic circuit for effecting a unidirectional actuation of said pistonan exhaust conduit oppositely coupled with the piston for conveying hydraulic actuating medium displaced thereby, a pair of alternatively available exhaust conduits, means for effecting low resistance to flow in one of said conduits, means for effecting higher resistance to ow in the other of said conduits, a

coupling of the piston exhaust conduit with respect to the low resistance exhaust conduit, whereby feed or rapid traverse movements of the piston mayA be effected under given actuating pressure according to the high or low resistance' exhaust conduit reaction thereon, additional means for bypassing the high pressure resistance to permit increased rate of discharge of the actuating medium by way of the high pressure resistance conduity and additional means for blocking the flow through the high resistance conduit.

12. The combination with a pair of relatively movable support elements and a servo-mechanism including relatively displacable parts for controlling the movement of said element, of means for determining cycle actuation of the servo-mechanism, including a selector valve, means serially coupling the selector valve with the servo-mechanism, a normally closed cycle determining valve for hydraulic actuation by way of the valve upon activating displacement of the servoelements, an auxiliary hydraulic actuating motor for said servo-elements and control circuits for said motor coupled with and completable by way of the cycle valve upon hydraulic actuation thereof.

13. The combination with a pair of relatively movable support elements and a servo-mechanism including relatively displacable parts for controlling the movement of said element, of means for determining cycle actuation of the servo-mechanism, including a selector valve, means serially coupling the selector valve with the servo-mechanism, a normally closed cycle determining valve for hydraulic actuation by way of the valve upon activating displacement of the servo-elements, an auxiliary hydraulic actuating motor for said servo-elements, control circuits for said motor coupled with and completable by Way of the cycle valve upon hydraulic actuation thereof, said control circuits including a Alow resistance exhaust conduit and a second exhaust conduit including a variable throttling resistance, a rst means actuable by the motor for controlling the exhaust flow through the low pressure conduit, and additional means for bypassing the throttling resista-nce in the other conduit to lower the resistance to flow therethrough substantially as and for the purpose described.

14. In a machine of the character described, the combination with a servo-control mechanism including relatively shiftable parts, of means for effecting a cycle movement of said relatively shiftable parts including an auxiliary hydraulic motor, a hydraulic operating circuit for said motor including a cycle control valve, and means for determining the circuit completing eiective position of the cycle control valve as respects the hydraulic motor including a cycle selector valve serially interposed between the cycle valve and the servo-members and positionable hydraulically to couple actuating medium from the servo to position the cycle valve upon relative activating movement of the Vservo-elements in one pressure coupling direction.

15. In a machine of the character described, the combination with a servo-control mechanism including relatively shiftable parts, of means for effecting a cycle movement of said relatively shiftable parts including an auxiliary hydraulic motor, a hydraulic operating circuit for said motor including a cycle control valve, means for determining the circuit completing effective posiselector device for determining the effective tion of the cycle control valve as respects the hydraulic motor/including a cycle selector Valve serially interposed between.. the cycle Valve and the servo-members and positionable hydraulically'j to couple actuating medium from the servo toY position the cycle valve upon relative activating. movement of the servos-elements in one pres- Sure coupling directon, means for eiectng an opposite directional positioningv of the cycle control valve to prevent activation of thev auxiliary control motor, and means for delaying the response of the cycle Valve to opposite positioningY 5 of the servo-elements.

RAYMOND D. WORTENDYKE. ANDREW J. GRAF. 

